Electrophotography charging device

ABSTRACT

A fulcrumed charging electrode to accurately space a corona generator wire or wires from a photoconductive surface for charging the same. The corona wire and associated shield are pivoted about an axis parallel to the wire and several specific means are shown for effecting the desired pivot action and adjustment.

United States Patent 1 1 Matsumoto et a].

ELECTROPHOTOGRAPHY CHARGING DEVICE Inventors: Seiji Matsumoto; ShigeruTezuka- Appl. No.: 319,117

[451 Mar. 26, 1974 [56] References Cited UNITED STATES PATENTS 2,790,0824/1957 Gundlach 250/325 2,882,412 4/1959 Cunningham 317/262 X VP45222.Ee m'ee w llieyli7.1429 1???.e

[ 5 7] ABSTRACT A fulcrumed charging electrode to accurately space acorona generator wire or wires from a photoconductive surface forcharging the same. The corona wire and associated shield are pivotedabout an axis paral- U.S. Cl. 250/325, 317/262 A 161 to the Wire andSeveral Specific means are shown i'i'iifl'f' sta. ass/5252 553342? feeeffeeeiee the deed eieee eee eejeeemem- 317/262 A 4 Claims, 3 DrawingFigures 7 8Q J; is b a: /4 /3 In 5: in In 5: ii 5 4 F o 3 g: I j n v: h5: 6 J u a: 5 I= vi h 5: /5 f 4 III I u 5 u is g 1 ELECTROPHOTOGRAPHYCHARGING DEVICE BACKGROUND OF THE INVENTION This invention relates toelectrophotography apparatus, and more particularly to a device forcontrolling the amount of charge uniformly distributed on aphotoconductive surface.

Xerographic processes and apparatus in general need not be described indetail herein, since various printed publications and patents areavailable in which these details are set forth. Examples of suchpublications are the books Electrophotography by R. M. Schaffert, andXerography and Related Processes by John H. Dessauer and Harold E.Clark, both first published in 1965: and the numerous patents and otherreferences cited in these books [All Jr'ihs references are herebyincorporated in this specification.

As is well-known in xerography, a photoconductive insulation is placedon a conductive surface and charged, usually by a corona dischargemeans, so that the photoconductive surface is at a certain potentialrelative to the grounded conductive plate. Upon exposure of this chargedphotoconductive surface, the photoconductive insulation becomesconductive and discharges its potential to the conductive groundedplate. The pattern of this electrical discharge is the pattern of theobject which is being exposed; i.e., an electrostatic image.

It is important to the quality of the electrostatic image that thecharge imparted to the photoconductive surface be uniform. In addition,it is desirable that the apparatus for effecting such charging beadjustable to compensate for various conditions of the chargingapparatus itself, the photoconductive surface, the photoconductivesurface, the atmosphere, the toner to be used, and other variables.

SUMMARY OF THE INVENTION It is an object of the present invention toprovide a photoconductor charging means, specifically a corona generatorapparatus, with associated mechanism for adjusting the level of chargeimparted to the photoconductor.

Briefly, the present invention is practiced in general by a chargingelectrode, including a corona wire and associated shield, disposed forpivotal movement relative to a photoconductive surface about an axisparallel to the corona wire.

For a better understanding of this invention, reference is made to thefollowing detailed description given in connection with the accompanyingdrawings.

DRAWINGS FIG. 1 is a somewhat schematic view of a charging electrode andphotoconductor according to one embodiment of this invention.

FIG. 2 is a perspective view showing a second embodiment of thisinvention.

FIG. 3 is a perspective view showing a third embodiment of thisinvention.

DESCRIPTION Referring now to FIG. 1, a photoconductive surface is shownat 1 and is mounted on a grounded conductive surface or plate 2. Acharging electrode apparatus is generally shown at 3 and includes one ormore corona wires 4, 4', 4" extending along or across the plane of thephotoconductor l and parallel thereto. A grounded corona shield 6 isdisposed in semi-enclosing relationship to the corona wires, andincludes separators 5', 5", and 5" extending between individual coronawires 4 and creating, in effect, separate corona shields.

The charging electrode 3 is supported on a lever arm mechanism 7 whichis in turn pivotally mounted on a fulcrum 8 which is on an axis parallelto that of the corona wire 4. Lever arm 7 and charging electrode 3traverse an arcuate locus, respectively indicated at 10 and 9, about thefulcrum 8.

In the FIG. 1 embodiment, this movement of lever arm 7 and electrode 3is controlled by a screw 12 which is operatively associated with a fixedframe member 11 and is in abutting relationship against the lever arm 7.Return movement of the lever arm 7 against the screw member 12 isprovided by a compression spring 14 which is mounted between lever arm 7and another fixed frame member or abutment 13.

In operation, it will be apparent that by adjusting the screw 12 in adesired direction, the charging electrode 3 with wires 4 and shield 6are all swung together toward or away from the photoconductor 1. By thismeans, a fine adjustment of the charge level on the photoconductivesurface can be made.

Referring now to FIG. 2, the lever arm 7 connected to the chargingelectrode 3 is in contact with a cam 20 which is connected to a shaft 21and a control handle 22. Shaft 21 is laterally offset from the fulcrum 8so that when shaft 21 and cam 20 are rotated, the result is to move thelever arm 7 about the fulcrum 8 with the same result as described inconnection with FIG. 1.

Referring now to FIG. 3, the lever arm 7 is provided at one end with agear sector 24 which engages with a worm gear 23 which in turn ismounted on a shaft 25 having a control handle 22. The gear actionbetween worm gear 23 and gear sector 24 motivates the lever arm 7 andcharging electrode 3 in the desired direction along its arcuate locus,similarly as described in connection with FIGS. 1 and 2.

In FIGS. 2 and 3, a spring device is shown mounted between the fulcrum 8and the lever 7 for the purpose of eliminating play in the mechanism.

It will be apparent that by use of the apparatus described in thisspecification, a charging electrode can be accurately positionedrelative to a charge-receptive surface.

The foregoing description of an embodiment of this invention is given byway of illustration and not of limitation. The concept and scope of theinvention are limited only by the following claims and equivalentsthereof which may occur to others skilled in the art.

What is claimed is:

l. A charging device for electrophotographic apparatus in which aphotoconductive surface is sensitized by the application thereto ofelectrostatic charge, said charging device including:

a grounded corona shield pivotally mounted to a frame for arcuatemovement relative to said photoconductive surface on an axis parallel tosaid photoconductive surface, said corona shield being thereby arcuatelydisplaceable toward and away from said photoconductive surface foradjustment of its operative position relative thereto,

said corona shield including an integral lever arm extending from saidaxis,

adjustment means mounted on said frame to variably cause said lever armand said corona shield to arcuately displace about said axis,

a corona wire supported within, and insulated from, said corona shieldand extending parallel to said axis,

the locus of all points on the arcuate path of said corona wireintersecting said photoconductive surface,

whereby said corona wire is adjustably movable toward and away from saidphotoconductive surface to increase and decrease, respectively, thelevel of electrostatic charge applied to said photoconductive surface.

2. A charging device as defined in claim 1 in which said adjustmentmeans includes:

a frame-mounted screw bearing against said lever arm and adjustablerelative to its mount to effect movement of said lever arm, and

a frame-mounted spring biasing said lever arm against said screw.

3. A charging device as defined in claim 1 in which said adjustmentmeans includes:

a cam rotatably mounted relative to said frame and bearing against saidlever arm, said cam effecting displacement of said lever arm in responseto rotation of said cam.

4. A charging device as defined in claim 1 in which said adjustmentmeans includes:

a first gear integral with said lever arm,

a second gear rotatably mounted relative to said frame and mating withsaid first gear, said first and second gears coacting to effectdisplacement of said lever arm in response to action of said secondgear.

1. A charging device for electrophotographic apparatus in which aphotoconductive surface is sensitized by the application thereto ofelectrostatic charge, said charging device including: a grounded coronashield pivotally mounted to a frame for arcuate movement relative tosaid photoconductive surface on an axis parallel to said photoconductivesurface, said corona shield being thereby arcuately displaceable towardand away from said photoconductive surface for adjustment of itsoperative position relative thereto, said corona shield including anintegral lever arm extending from said axis, adjustment means mounted onsaid frame to variably cause said lever arm and said corona shield toarcuately displace about said axis, a corona wire supported within, andinsulated from, said corona shield and extending parallel to said axis,the locus of all points on the arcuate path of said corona wireintersecting said photoconductive surface, whereby said corona wire isadjustably movable toward and away from said photoconductive surface toincrease and decrease, respectively, the level of electrostatic chargeapplied to said photoconductive surface.
 2. A charging device as definedin claim 1 in which said adjustment means includes: a frame-mountedscrew bearing against said lever arm and adjustable relative to itsmount to effect movement of said lever arm, and a frame-mounted springbiasing said lever arm against said screw.
 3. A charging device asdefined in claim 1 in which said adjUstment means includes: a camrotatably mounted relative to said frame and bearing against said leverarm, said cam effecting displacement of said lever arm in response torotation of said cam.
 4. A charging device as defined in claim 1 inwhich said adjustment means includes: a first gear integral with saidlever arm, a second gear rotatably mounted relative to said frame andmating with said first gear, said first and second gears coacting toeffect displacement of said lever arm in response to action of saidsecond gear.